<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
  <!-- '-'连接单词,但描述的还是同一个个体 -->
  <div class="x-ui">
    <!-- 用'--'表修饰 -->
    <!-- 'is-xxx'表状态 -->
    <button class="x-ui--primary is-readonly is-disabled"></button>
    <button class="x-ui--success"></button>
    <button class="x-ui--primary"></button>

    <!-- 用'__'进行元素分割 -->
    <div class="x-ui__header"></div>
    <div class="x-ui__body"></div>
    <div class="x-ui__footer"></div>
  </div>
</body>
</html>
